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    <div class="post-body" itemprop="articleBody"><p>mitt 是一个非常小巧的库，在写 vue3 和微信小程序的时候也经常用到，这里先上转成 js 的代码：</p>
<span id="more"></span>

<h1 id="源码"><a href="#源码" class="headerlink" title="源码"></a>源码</h1><figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">export</span> <span class="keyword">default</span> <span class="keyword">function</span> <span class="title function_">mitt</span>(<span class="params">all</span>) &#123;</span><br><span class="line">  all = all || <span class="keyword">new</span> <span class="title class_">Map</span>()</span><br><span class="line">  <span class="keyword">return</span> &#123;</span><br><span class="line">    <span class="comment">/**</span></span><br><span class="line"><span class="comment">     * A Map of event names to registered handler functions.</span></span><br><span class="line"><span class="comment">     * 从事件名到handler回调的映射</span></span><br><span class="line"><span class="comment">     */</span></span><br><span class="line">    all,</span><br><span class="line">    <span class="comment">/**</span></span><br><span class="line"><span class="comment">     * Register an event handler for the given type.</span></span><br><span class="line"><span class="comment">     * 根据type注册一个handler</span></span><br><span class="line"><span class="comment">     * <span class="doctag">@param</span> &#123;<span class="type">string|symbol</span>&#125; type Type of event to listen for, or `&#x27;*&#x27;` for all events | 需要监听的事件名，`&#x27;*&#x27;`代表所有事件</span></span><br><span class="line"><span class="comment">     * <span class="doctag">@param</span> &#123;<span class="type">Function</span>&#125; handler Function to call in response to given event | 对应的回调</span></span><br><span class="line"><span class="comment">     * <span class="doctag">@memberOf</span> <span class="variable">mitt</span></span></span><br><span class="line"><span class="comment">     */</span></span><br><span class="line">    <span class="title function_">on</span>(<span class="params">type, handler</span>) &#123;</span><br><span class="line">      <span class="keyword">const</span> handlers = all.<span class="title function_">get</span>(type)</span><br><span class="line">      <span class="keyword">if</span> (handlers) &#123;</span><br><span class="line">        handlers.<span class="title function_">push</span>(handler)</span><br><span class="line">      &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">        all.<span class="title function_">set</span>(type, [handler])</span><br><span class="line">      &#125;</span><br><span class="line">    &#125;,</span><br><span class="line">    <span class="comment">/**</span></span><br><span class="line"><span class="comment">     * Remove an event handler for the given type.</span></span><br><span class="line"><span class="comment">     * 去除指定事件名的指定handler</span></span><br><span class="line"><span class="comment">     * If `handler` is omitted, all handlers of the given type are removed.</span></span><br><span class="line"><span class="comment">     * 如果不提供handler，将会去除所有该事件的hanlder</span></span><br><span class="line"><span class="comment">     * <span class="doctag">@param</span> &#123;<span class="type">string|symbol</span>&#125; type Type of event to unregister `handler` from (`&#x27;*&#x27;` to remove a wildcard handler)</span></span><br><span class="line"><span class="comment">     * <span class="doctag">@param</span> &#123;<span class="type">Function</span>&#125; [handler] Handler function to remove</span></span><br><span class="line"><span class="comment">     * <span class="doctag">@memberOf</span> <span class="variable">mitt</span></span></span><br><span class="line"><span class="comment">     */</span></span><br><span class="line">    <span class="title function_">off</span>(<span class="params">type, handler</span>) &#123;</span><br><span class="line">      <span class="keyword">const</span> handlers = all.<span class="title function_">get</span>(type)</span><br><span class="line">      <span class="keyword">if</span> (handlers) &#123;</span><br><span class="line">        <span class="keyword">if</span> (handler) &#123;</span><br><span class="line">          handlers.<span class="title function_">splice</span>(handlers.<span class="title function_">indexOf</span>(handler) &gt;&gt;&gt; <span class="number">0</span>, <span class="number">1</span>)</span><br><span class="line">        &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">          all.<span class="title function_">set</span>(type, [])</span><br><span class="line">        &#125;</span><br><span class="line">      &#125;</span><br><span class="line">    &#125;,</span><br><span class="line">    <span class="comment">/**</span></span><br><span class="line"><span class="comment">     * Invoke all handlers for the given type.</span></span><br><span class="line"><span class="comment">     * 触发type的所有handler</span></span><br><span class="line"><span class="comment">     * If present, `&#x27;*&#x27;` handlers are invoked after type-matched handlers.</span></span><br><span class="line"><span class="comment">     * `&#x27;*&#x27;` 的 handler 会在type匹配的handler执行完后执行</span></span><br><span class="line"><span class="comment">     * Note: Manually firing &#x27;*&#x27; handlers is not supported.</span></span><br><span class="line"><span class="comment">     * 手动提供&#x27;*&#x27;是不不支持的</span></span><br><span class="line"><span class="comment">     *</span></span><br><span class="line"><span class="comment">     * <span class="doctag">@param</span> &#123;<span class="type">string|symbol</span>&#125; type The event type to invoke</span></span><br><span class="line"><span class="comment">     * <span class="doctag">@param</span> &#123;<span class="type">Any</span>&#125; [evt] Any value (object is recommended and powerful), passed to each handler</span></span><br><span class="line"><span class="comment">     * <span class="doctag">@memberOf</span> <span class="variable">mitt</span></span></span><br><span class="line"><span class="comment">     */</span></span><br><span class="line">    <span class="title function_">emit</span>(<span class="params">type, evt</span>) &#123;</span><br><span class="line">      <span class="keyword">let</span> handlers = all.<span class="title function_">get</span>(type)</span><br><span class="line">      <span class="keyword">if</span> (handlers) &#123;</span><br><span class="line">        handlers.<span class="title function_">slice</span>().<span class="title function_">map</span>(<span class="function">(<span class="params">handler</span>) =&gt;</span> &#123;</span><br><span class="line">          <span class="title function_">handler</span>(evt)</span><br><span class="line">        &#125;)</span><br><span class="line">      &#125;</span><br><span class="line">      handlers = all.<span class="title function_">get</span>(<span class="string">&#x27;*&#x27;</span>)</span><br><span class="line">      <span class="keyword">if</span> (handlers) &#123;</span><br><span class="line">        handlers.<span class="title function_">slice</span>().<span class="title function_">map</span>(<span class="function">(<span class="params">handler</span>) =&gt;</span> &#123;</span><br><span class="line">          <span class="title function_">handler</span>(type, evt)</span><br><span class="line">        &#125;)</span><br><span class="line">      &#125;</span><br><span class="line">    &#125;,</span><br><span class="line">  &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>

<h1 id="ts-版"><a href="#ts-版" class="headerlink" title="ts 版"></a>ts 版</h1><figure class="highlight ts"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br><span class="line">79</span><br><span class="line">80</span><br><span class="line">81</span><br><span class="line">82</span><br><span class="line">83</span><br><span class="line">84</span><br><span class="line">85</span><br><span class="line">86</span><br><span class="line">87</span><br><span class="line">88</span><br><span class="line">89</span><br><span class="line">90</span><br><span class="line">91</span><br><span class="line">92</span><br><span class="line">93</span><br><span class="line">94</span><br><span class="line">95</span><br><span class="line">96</span><br><span class="line">97</span><br><span class="line">98</span><br><span class="line">99</span><br><span class="line">100</span><br><span class="line">101</span><br><span class="line">102</span><br><span class="line">103</span><br><span class="line">104</span><br><span class="line">105</span><br><span class="line">106</span><br><span class="line">107</span><br><span class="line">108</span><br><span class="line">109</span><br><span class="line">110</span><br><span class="line">111</span><br><span class="line">112</span><br><span class="line">113</span><br><span class="line">114</span><br><span class="line">115</span><br><span class="line">116</span><br><span class="line">117</span><br><span class="line">118</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">export</span> <span class="keyword">type</span> <span class="title class_">EventType</span> = <span class="built_in">string</span> | <span class="built_in">symbol</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// 普通handler</span></span><br><span class="line"><span class="keyword">export</span> <span class="keyword">type</span> <span class="title class_">Handler</span>&lt;T = <span class="built_in">unknown</span>&gt; = <span class="function">(<span class="params">event: T</span>) =&gt;</span> <span class="built_in">void</span></span><br><span class="line"><span class="comment">// 通配符handler</span></span><br><span class="line"><span class="keyword">export</span> <span class="keyword">type</span> <span class="title class_">WildcardHandler</span>&lt;T = <span class="title class_">Record</span>&lt;<span class="built_in">string</span>, <span class="built_in">unknown</span>&gt;&gt; = <span class="function">(<span class="params"></span></span></span><br><span class="line"><span class="params"><span class="function">  <span class="keyword">type</span>: keyof T,</span></span></span><br><span class="line"><span class="params"><span class="function">  event: T[keyof T]</span></span></span><br><span class="line"><span class="params"><span class="function"></span>) =&gt;</span> <span class="built_in">void</span></span><br><span class="line"></span><br><span class="line"><span class="keyword">export</span> <span class="keyword">type</span> <span class="title class_">EventHandlerList</span>&lt;T = <span class="built_in">unknown</span>&gt; = <span class="title class_">Array</span>&lt;<span class="title class_">Handler</span>&lt;T&gt;&gt;</span><br><span class="line"><span class="keyword">export</span> <span class="keyword">type</span> <span class="title class_">WildCardEventHandlerList</span>&lt;T = <span class="title class_">Record</span>&lt;<span class="built_in">string</span>, <span class="built_in">unknown</span>&gt;&gt; = <span class="title class_">Array</span>&lt;</span><br><span class="line">  <span class="title class_">WildcardHandler</span>&lt;T&gt;</span><br><span class="line">&gt;</span><br><span class="line"></span><br><span class="line"><span class="keyword">export</span> <span class="keyword">type</span> <span class="title class_">EventHandlerMap</span>&lt;<span class="title class_">Events</span> <span class="keyword">extends</span> <span class="title class_">Record</span>&lt;<span class="title class_">EventType</span>, <span class="built_in">unknown</span>&gt;&gt; = <span class="title class_">Map</span>&lt;</span><br><span class="line">  keyof <span class="title class_">Events</span> | <span class="string">&#x27;*&#x27;</span>,</span><br><span class="line">  <span class="title class_">EventHandlerList</span>&lt;<span class="title class_">Events</span>[keyof <span class="title class_">Events</span>]&gt; | <span class="title class_">WildCardEventHandlerList</span>&lt;<span class="title class_">Events</span>&gt;</span><br><span class="line">&gt;</span><br><span class="line"></span><br><span class="line"><span class="keyword">export</span> <span class="keyword">interface</span> <span class="title class_">Emitter</span>&lt;<span class="title class_">Events</span> <span class="keyword">extends</span> <span class="title class_">Record</span>&lt;<span class="title class_">EventType</span>, <span class="built_in">unknown</span>&gt;&gt; &#123;</span><br><span class="line">  <span class="attr">all</span>: <span class="title class_">EventHandlerMap</span>&lt;<span class="title class_">Events</span>&gt;</span><br><span class="line"></span><br><span class="line">  on&lt;<span class="title class_">Key</span> <span class="keyword">extends</span> keyof <span class="title class_">Events</span>&gt;(<span class="attr">type</span>: <span class="title class_">Key</span>, <span class="attr">handler</span>: <span class="title class_">Handler</span>&lt;<span class="title class_">Events</span>[<span class="title class_">Key</span>]&gt;): <span class="built_in">void</span></span><br><span class="line">  <span class="title function_">on</span>(<span class="attr">type</span>: <span class="string">&#x27;*&#x27;</span>, <span class="attr">handler</span>: <span class="title class_">WildcardHandler</span>&lt;<span class="title class_">Events</span>&gt;): <span class="built_in">void</span></span><br><span class="line"></span><br><span class="line">  off&lt;<span class="title class_">Key</span> <span class="keyword">extends</span> keyof <span class="title class_">Events</span>&gt;(<span class="attr">type</span>: <span class="title class_">Key</span>, handler?: <span class="title class_">Handler</span>&lt;<span class="title class_">Events</span>[<span class="title class_">Key</span>]&gt;): <span class="built_in">void</span></span><br><span class="line">  <span class="title function_">off</span>(<span class="attr">type</span>: <span class="string">&#x27;*&#x27;</span>, <span class="attr">handler</span>: <span class="title class_">WildcardHandler</span>&lt;<span class="title class_">Events</span>&gt;): <span class="built_in">void</span></span><br><span class="line"></span><br><span class="line">  emit&lt;<span class="title class_">Key</span> <span class="keyword">extends</span> keyof <span class="title class_">Events</span>&gt;(<span class="attr">type</span>: <span class="title class_">Key</span>, <span class="attr">event</span>: <span class="title class_">Events</span>[<span class="title class_">Key</span>]): <span class="built_in">void</span></span><br><span class="line">  emit&lt;<span class="title class_">Key</span> <span class="keyword">extends</span> keyof <span class="title class_">Events</span>&gt;(</span><br><span class="line">    <span class="attr">type</span>: <span class="literal">undefined</span> <span class="keyword">extends</span> <span class="title class_">Events</span>[<span class="title class_">Key</span>] ? <span class="title class_">Key</span> : <span class="built_in">never</span></span><br><span class="line">  ): <span class="built_in">void</span></span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">/**</span></span><br><span class="line"><span class="comment"> * Mitt: Tiny (~200b) functional event emitter / pubsub.</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@name</span> <span class="variable">mitt</span></span></span><br><span class="line"><span class="comment"> * <span class="doctag">@returns</span> &#123;<span class="type">Mitt</span>&#125;</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="keyword">export</span> <span class="keyword">default</span> <span class="keyword">function</span> mitt&lt;<span class="title class_">Events</span> <span class="keyword">extends</span> <span class="title class_">Record</span>&lt;<span class="title class_">EventType</span>, <span class="built_in">unknown</span>&gt;&gt;(</span><br><span class="line">  all?: <span class="title class_">EventHandlerMap</span>&lt;<span class="title class_">Events</span>&gt;</span><br><span class="line">): <span class="title class_">Emitter</span>&lt;<span class="title class_">Events</span>&gt; &#123;</span><br><span class="line">  <span class="keyword">type</span> <span class="title class_">GenericEventHandler</span> =</span><br><span class="line">    | <span class="title class_">Handler</span>&lt;<span class="title class_">Events</span>[keyof <span class="title class_">Events</span>]&gt;</span><br><span class="line">    | <span class="title class_">WildcardHandler</span>&lt;<span class="title class_">Events</span>&gt;</span><br><span class="line">  all = all || <span class="keyword">new</span> <span class="title class_">Map</span>()</span><br><span class="line"></span><br><span class="line">  <span class="keyword">return</span> &#123;</span><br><span class="line">    <span class="comment">/**</span></span><br><span class="line"><span class="comment">     * A Map of event names to registered handler functions.</span></span><br><span class="line"><span class="comment">     */</span></span><br><span class="line">    all,</span><br><span class="line"></span><br><span class="line">    <span class="comment">/**</span></span><br><span class="line"><span class="comment">     * Register an event handler for the given type.</span></span><br><span class="line"><span class="comment">     * <span class="doctag">@param</span> &#123;<span class="type">string|symbol</span>&#125; type Type of event to listen for, or `&#x27;*&#x27;` for all events</span></span><br><span class="line"><span class="comment">     * <span class="doctag">@param</span> &#123;<span class="type">Function</span>&#125; handler Function to call in response to given event</span></span><br><span class="line"><span class="comment">     * <span class="doctag">@memberOf</span> <span class="variable">mitt</span></span></span><br><span class="line"><span class="comment">     */</span></span><br><span class="line">    on&lt;<span class="title class_">Key</span> <span class="keyword">extends</span> keyof <span class="title class_">Events</span>&gt;(<span class="attr">type</span>: <span class="title class_">Key</span>, <span class="attr">handler</span>: <span class="title class_">GenericEventHandler</span>) &#123;</span><br><span class="line">      <span class="keyword">const</span> <span class="attr">handlers</span>: <span class="title class_">Array</span>&lt;<span class="title class_">GenericEventHandler</span>&gt; | <span class="literal">undefined</span> = all!.<span class="title function_">get</span>(<span class="keyword">type</span>)</span><br><span class="line">      <span class="keyword">if</span> (handlers) &#123;</span><br><span class="line">        handlers.<span class="title function_">push</span>(handler)</span><br><span class="line">      &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">        all!.<span class="title function_">set</span>(<span class="keyword">type</span>, [handler] <span class="keyword">as</span> <span class="title class_">EventHandlerList</span>&lt;<span class="title class_">Events</span>[keyof <span class="title class_">Events</span>]&gt;)</span><br><span class="line">      &#125;</span><br><span class="line">    &#125;,</span><br><span class="line"></span><br><span class="line">    <span class="comment">/**</span></span><br><span class="line"><span class="comment">     * Remove an event handler for the given type.</span></span><br><span class="line"><span class="comment">     * If `handler` is omitted, all handlers of the given type are removed.</span></span><br><span class="line"><span class="comment">     * <span class="doctag">@param</span> &#123;<span class="type">string|symbol</span>&#125; type Type of event to unregister `handler` from (`&#x27;*&#x27;` to remove a wildcard handler)</span></span><br><span class="line"><span class="comment">     * <span class="doctag">@param</span> &#123;<span class="type">Function</span>&#125; [handler] Handler function to remove</span></span><br><span class="line"><span class="comment">     * <span class="doctag">@memberOf</span> <span class="variable">mitt</span></span></span><br><span class="line"><span class="comment">     */</span></span><br><span class="line">    off&lt;<span class="title class_">Key</span> <span class="keyword">extends</span> keyof <span class="title class_">Events</span>&gt;(<span class="attr">type</span>: <span class="title class_">Key</span>, handler?: <span class="title class_">GenericEventHandler</span>) &#123;</span><br><span class="line">      <span class="keyword">const</span> <span class="attr">handlers</span>: <span class="title class_">Array</span>&lt;<span class="title class_">GenericEventHandler</span>&gt; | <span class="literal">undefined</span> = all!.<span class="title function_">get</span>(<span class="keyword">type</span>)</span><br><span class="line">      <span class="keyword">if</span> (handlers) &#123;</span><br><span class="line">        <span class="keyword">if</span> (handler) &#123;</span><br><span class="line">          handlers.<span class="title function_">splice</span>(handlers.<span class="title function_">indexOf</span>(handler) &gt;&gt;&gt; <span class="number">0</span>, <span class="number">1</span>)</span><br><span class="line">        &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">          all!.<span class="title function_">set</span>(<span class="keyword">type</span>, [])</span><br><span class="line">        &#125;</span><br><span class="line">      &#125;</span><br><span class="line">    &#125;,</span><br><span class="line"></span><br><span class="line">    <span class="comment">/**</span></span><br><span class="line"><span class="comment">     * Invoke all handlers for the given type.</span></span><br><span class="line"><span class="comment">     * If present, `&#x27;*&#x27;` handlers are invoked after type-matched handlers.</span></span><br><span class="line"><span class="comment">     *</span></span><br><span class="line"><span class="comment">     * Note: Manually firing &#x27;*&#x27; handlers is not supported.</span></span><br><span class="line"><span class="comment">     *</span></span><br><span class="line"><span class="comment">     * <span class="doctag">@param</span> &#123;<span class="type">string|symbol</span>&#125; type The event type to invoke</span></span><br><span class="line"><span class="comment">     * <span class="doctag">@param</span> &#123;<span class="type">Any</span>&#125; [evt] Any value (object is recommended and powerful), passed to each handler</span></span><br><span class="line"><span class="comment">     * <span class="doctag">@memberOf</span> <span class="variable">mitt</span></span></span><br><span class="line"><span class="comment">     */</span></span><br><span class="line">    emit&lt;<span class="title class_">Key</span> <span class="keyword">extends</span> keyof <span class="title class_">Events</span>&gt;(<span class="attr">type</span>: <span class="title class_">Key</span>, evt?: <span class="title class_">Events</span>[<span class="title class_">Key</span>]) &#123;</span><br><span class="line">      <span class="keyword">let</span> handlers = all!.<span class="title function_">get</span>(<span class="keyword">type</span>)</span><br><span class="line">      <span class="keyword">if</span> (handlers) &#123;</span><br><span class="line">        ;(handlers <span class="keyword">as</span> <span class="title class_">EventHandlerList</span>&lt;<span class="title class_">Events</span>[keyof <span class="title class_">Events</span>]&gt;)</span><br><span class="line">          .<span class="title function_">slice</span>()</span><br><span class="line">          .<span class="title function_">map</span>(<span class="function">(<span class="params">handler</span>) =&gt;</span> &#123;</span><br><span class="line">            <span class="title function_">handler</span>(evt!)</span><br><span class="line">          &#125;)</span><br><span class="line">      &#125;</span><br><span class="line"></span><br><span class="line">      handlers = all!.<span class="title function_">get</span>(<span class="string">&#x27;*&#x27;</span>)</span><br><span class="line">      <span class="keyword">if</span> (handlers) &#123;</span><br><span class="line">        ;(handlers <span class="keyword">as</span> <span class="title class_">WildCardEventHandlerList</span>&lt;<span class="title class_">Events</span>&gt;)</span><br><span class="line">          .<span class="title function_">slice</span>()</span><br><span class="line">          .<span class="title function_">map</span>(<span class="function">(<span class="params">handler</span>) =&gt;</span> &#123;</span><br><span class="line">            <span class="title function_">handler</span>(<span class="keyword">type</span>, evt!)</span><br><span class="line">          &#125;)</span><br><span class="line">      &#125;</span><br><span class="line">    &#125;,</span><br><span class="line">  &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>

<p>用法：</p>
<figure class="highlight ts"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">type</span> <span class="title class_">Events</span> = &#123;</span><br><span class="line">  <span class="attr">emitString</span>: <span class="built_in">string</span></span><br><span class="line">  <span class="attr">emitVoid</span>: <span class="built_in">void</span></span><br><span class="line">&#125;</span><br><span class="line"><span class="keyword">const</span> emitter = mitt&lt;<span class="title class_">Events</span>&gt;()</span><br><span class="line">emitter.<span class="title function_">on</span>(<span class="string">&#x27;emitVoid&#x27;</span>, <span class="function">()=&gt;</span>&#123;</span><br><span class="line">  <span class="variable language_">console</span>.<span class="title function_">log</span>(<span class="string">&#x27;emitVoid&#x27;</span>)</span><br><span class="line">&#125;)</span><br><span class="line">emitter.<span class="title function_">on</span>(<span class="string">&#x27;emitString&#x27;</span>, <span class="function">(<span class="params">str</span>)=&gt;</span>&#123;</span><br><span class="line">  <span class="variable language_">console</span>.<span class="title function_">log</span>(str)</span><br><span class="line">&#125;)</span><br><span class="line">emitter.<span class="title function_">emit</span>(<span class="string">&#x27;emitVoid&#x27;</span>)</span><br><span class="line">emitter.<span class="title function_">emit</span>(<span class="string">&#x27;emitString&#x27;</span>, <span class="string">&#x27;test&#x27;</span>)</span><br></pre></td></tr></table></figure>
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